JP2000009973A - Optical fiber bundle and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a polarization maintaining characteristic by using an adhesive having a small Young's modulus as the adhesive of a fiber bundle formed by inserting polarization maintaining fibers unified in a polarization direction into a capillary and solidifying the fibers with the adhesive and to prevent the occurrence of chipping at the optical fiber end faces at the time of polishing the front end faces even in the case of the low hardness of the small Young's modulus thereof small. SOLUTION: The adhesive 30A of the high hardness to the extent of not giving rise to the chipping at the time of polishing (having the large Young's modulus as well) is packed to the front end of the capillary 20 and the adhesive 30B of the small Young's modulus to the extent of not imparting a stress and strain to the optical fibers after curing is packed in the portions exclusive thereof. The greater part of the position packed with the adhesive 30A of the high hardness is chipped away in a polishing stage at the time of production. There is substantially no influence of the adhesive 30A having the high hardness and the large Young's modulus in the product and the polarization maintaining characteristic is good.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization-maintaining optical fiber bundle, and an apparatus using the same is used as a component of an optical signal processing system using polarization.

[0002]

2. Description of the Related Art A polarization-maintaining optical fiber is arranged in a capillary (capillary tube) and arranged at least at the end face of the optical fiber bundle so that the polarization directions of the respective polarization-maintaining optical fibers are aligned. There has been proposed an optical fiber bundle formed by bonding a wave holding optical fiber and a capillary with an adhesive.

[0003]

The properties of the adhesive include:
There are items of hardness and Young's modulus. For use in bundling a polarization maintaining optical fiber, one having high hardness and low Young's modulus is desirable. The reason is as follows.

That is, if the hardness is small, the optical fiber core wire vibrates when polishing the end face of the capillary,
Chipping occurs in the end face of the optical fiber. When chipping occurs, problems such as deterioration of polarization maintaining characteristics and cracks resulting in increased loss occur. In addition, if the Young's modulus after curing is large, uneven stress is applied to the optical fiber, causing a problem that the polarization maintaining characteristic is deteriorated.

However, there is generally no resin (adhesive) having high hardness and low Young's modulus. Generally, the higher the hardness, the higher the Young's modulus, and the lower the Young's modulus, the lower the hardness. It is difficult to solve these problems at the same time.

[0006]

According to the present invention, as shown in FIG. 1, the tip of the capillary 20 (the right end in FIGS. 1 (a) and 1 (b)) is chipped during polishing. An adhesive 30A having a large hardness that does not cause the above-mentioned problem is filled, and an adhesive 30B having a small Young's modulus that does not give stress distortion to the optical fiber after curing is filled up to the other end.

[0007] In a polishing step at the time of manufacture, most of the portion filled with the high-hardness adhesive 30A is scraped off, and the high-hardness adhesive 3A is formed in a bundle as a product.
The effect of 0A is almost eliminated.

If the adhesive has a low Young's modulus that does not give stress distortion to the optical fiber after curing, the extinction ratio of each polarization-maintaining optical fiber before bundling and the entire bundle after bundling Extinction ratios can be about the same.

More specifically, as the adhesive 30B having a small Young's modulus, an adhesive having a Young's modulus after curing of 6 MPa or less is used, and the extinction ratio after bundling is maintained at -40 dB to -50 dB. It is desirable to be able to do so.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Object itself] At the ends of a plurality of polarization-maintaining optical fiber cores 10, the coating 12 is removed by about several mm (FIG. 1A), and the bare fiber 14 is polarized. It is inserted into the capillary 20 with the wave axes aligned, preferably in a close-packed state. The material of the capillary 20 is borosilicate glass, quartz, or the like, and is a material that transmits ultraviolet light when using an ultraviolet curable resin.

From the tip of the capillary 20, 0.2 to 0.3 mm
An approximately 30-degree portion is filled with a high-hardness adhesive 30A. The hardness of the adhesive is large enough not to cause chipping during polishing. Regarding the Young's modulus, its value does not matter. Here, the meaning of high hardness includes that the hardness is higher than that of the adhesive 30B.

The other parts are filled with an adhesive 30B having a small Young's modulus. After hardening, the Young's modulus is tossed so small as not to give stress strain to the optical fiber. Regardless of hardness

FIG. 1 (c) is an enlarged view schematically showing an end face, in which 15 is a core, 16 is a clad, and 18 is a stress applying section.

[Manufacturing method] The coating 12 on the end of the polarization maintaining optical fiber core wire 10 is removed. Multiple bare fibers 14
Are bundled round, and the polarization axes are aligned in a certain direction by observing the end face. An adhesive 30B having a small Young's modulus is applied or filled on a portion of the inner surface of the capillary 20 other than the tip of about 0.2 to 0.3 mm. The bare fiber 14 group also
Except for about 0.3 mm, the adhesive 30B having a small Young's modulus is applied or filled and inserted into the capillary 20.

Then, an adhesive 30A having a large hardness is applied or filled into the portion of the capillary 20 at the tip end where the adhesive is not contained, from the tip end surface.

Thereafter, it is checked whether or not the polarization axis is in a fixed direction, and if it is moving, it is rotated and adjusted before the adhesives 30A and 30B are hardened. After that, the adhesives 30A and 30B are cured.

Thereafter, the tip of the capillary 20 is polished. At this time, about 1 mm of the portion filled with the adhesive 30A having a high hardness remains, and the other portion is scraped off.

[0018]

EXAMPLE Three types of samples were produced, two types (A and B) according to the conventional method and one type according to the method of the present invention, and the occurrence ratio of fiber chipping at the end face and the polarization maintaining characteristics were evaluated. The extinction ratio was measured as the polarization maintaining characteristic. The smaller the value (the larger the value in the negative direction), the better the polarization maintaining characteristic.

In the method of the present invention, UV2100 (Daikin Industries, epoxy system, Shore hardness Hs = 80, preferably 80 or more) is used for the adhesive 30A having a high hardness. For 30B, FC-0708 (Dainippon Ink & Chemicals, acrylate type, Young's modulus = 6 MPa)
The following was used. Further, in the conventional method A, only one kind of the above-described adhesive 30A having a high hardness is used, and in the conventional method B,
Only one kind of the adhesive 30B having a small Young's modulus was used.

The polarization-maintaining optical fiber is a so-called panda-type, glass-based optical fiber.

As the adhesive, a photo-curing type is preferably used, but a room temperature-curing type, a one-component type, or a two-component type may be used. As the material, an epoxy-based or acrylate-based material can be suitably used.

The results are shown in the table below. Prototype Chip generation rate Extinction ratio (dB) Conventional method A 0/10 -10 ~ -30 Conventional method B 5/10 -35 ~ -50 Our method 0/10 / 10-35 ~ -50

According to the method of the present invention, fiber chipping at the end face becomes zero. Also, the value of the extinction ratio of −35 dB to −50 dB is almost the same as the value of the polarization-maintaining optical fiber alone before bundling, and it can be seen that the polarization maintaining characteristic does not deteriorate due to bundling.

[0024]

According to the present invention, it is possible to manufacture a fiber bundle in which the fiber at the end face is not chipped and the polarization maintaining characteristic is not deteriorated.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the present invention, wherein (a) shows a state before polishing viewed from a side, (b) shows a state after polishing similarly, and (c) shows a state where an end face is enlarged.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Polarization-maintaining optical fiber core wire 12 Coating 14 Bare fiber 15 Core 16 Cladding 18 Stress applying part 20 Capillary 30A Adhesive with high hardness 30B Adhesive with low Young's modulus

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideyuki Hosoya 1440, Misaki, Sakura-shi, Chiba F-term in Fujikura Sakura Plant (reference) 2H001 BB03 BB25

Claims (2)

[Claims] A polarization-maintaining optical fiber is arranged in a capillary, and the polarization-maintaining optical fibers are arranged at least at the end face of the optical fiber bundle so that the polarization directions of the polarization-maintaining optical fibers are aligned. In an optical fiber bundle formed by bonding an optical fiber and a capillary with an adhesive, two types of adhesives, a high hardness adhesive 30A and a low Young's modulus adhesive 30B, are used as the adhesive, and at the tip of the capillary, Fill the adhesive 30A with a hardness high enough not to cause chipping during polishing, and fill the other parts with an adhesive 30B having a small Young's modulus that does not give stress distortion to the optical fiber after curing. An optical fiber bundle, characterized in that: 2. A polarization-maintaining optical fiber is arranged in a capillary, and the polarization-maintaining optical fibers are arranged so that the polarization directions of the respective polarization-maintaining optical fibers are aligned at least at the end face of the optical fiber bundle. In a method of manufacturing an optical fiber bundle, wherein an optical fiber and a capillary are bonded with an adhesive and then the tip of the capillary is polished, the adhesive 30A having a hardness large enough not to cause chipping during polishing at the tip of the capillary. And other parts are filled with an adhesive 30B having a small Young's modulus that does not give stress distortion to the optical fiber after curing, and in the polishing step, the adhesive 30A having the high hardness is filled. A method for producing an optical fiber bundle, characterized in that a large part of the portion is cut off.